The present invention relates to downhole gripping tools commonly used in the hydrocarbon recovery industry to anchor a tool within a downhole tubular. In particular, the present invention relates to improved method for releasing the slip setting mechanism upon rotation of the work string in one direction, while also insuring that the slip setting mechanism is not damaged in the event of rotation of the running string or work string in the opposite direction.
Downhole gripping tools, such as liner hangers, hook wall packers and anchors, commonly include circumferentially spaced slips which are moved radially outward into biting engagement with the interior diameter of the downhole tubular or the borehole wall upon axial movement of the tapered cone relative to the slips. The desired axial movement may be achieved with a hydraulic setting mechanism, but in many applications the set down weight to the running string is sufficient to achieve the desired axial movement and bring the slips into gripping engagement, thereby anchoring the gripping tool within the well. In a subsequent application of hydraulic pressure or through vertical manipulation of the running string, these slips may be disengaged, thereby releasing the anchored gripping tool from its position in the well. A liner hanger, packer, or other gripping tool may thus be run in the well on a work string, positioned at a desired location within the downhole tubular or open well bore, and then set to at least temporarily affix the gripping tool to the downhole tubular within the well bore. A release mechanism is commonly provided to release the running string from the set downhole gripping tool, so that the running string may be returned to the surface and, if desired, another tool or tubular passed through the bore of the set gripping tool.
Many mechanically set gripping tools have utilized two successive or sequential rotational movements in opposite directions to release the slips and thereafter bring the gripping tool into fixed engagement within the well, and to release the set gripping tool from the running string. One rotation may be used to release the slip setting mechanism, and another rotational movement may be used to release the running string from the set downhole tool. Left-hand rotation of the work string and thus the running tool may be used to initiate the release of the gripping tool to be moved to the set position, and then right-hand rotation of the work string and the running tool may be used to effect the release of the gripping tool so that running string may be returned to the surface. Any time left-hand rotation is applied to a right-hand threaded work string, there is the danger of unthreading one of the multiple joints, rather than the desired transmission of the rotational force through the multiple joints to the running tool. The release of the slip setting mechanism and the release of the tool from the work string may be in the same rotational direction, which preferably is the same as the threaded connections of the work string. U.S. Pat. No. 4,709,758 discloses a packer which is released by rotation of the running string to position a J-pin in an axially elongated portion of a J-slot, followed by upward movement of the running string to compress the packing element to form a seal with the casing well and expand the slips.
Reliability of setting operation is paramount, since the consequences of a failed tool may cost hundreds of thousands of dollars. In addition, it is very important that the cone not move prematurely with respect to the slips, or that the slips not move outward before cone movement, which may cause the gripping tool to prematurely set in the well, or may allow teeth on the slips to get hung up in the well or damage a downhole sealing surface.
Slips on downhole tools are most commonly released from their run-in position and allowed to move to the engaged or set position by vertical manipulation of running string and thus vertical movement of the cone with respect to the slips. The cone may be secured to a mandrel which is threadably connected to the work string. The slips may be held stationary by a bowed slat stabilizer or other drag mechanism which engages the inner wall of the casing or well bore and resists axial movement with the work string. In many applications, a radially projecting pin secured to the mandrel fits within a J-slot in the outertool body to control movement of the slips from the run-in position to the released position and then to the set position by vertical manipulation of the work string. U.S. Pat. No. 6,241,017 discloses a packer which uses tension in a wireline to shear a connection. A collet is detachably secured to a threaded profile. Axial movement of the running string applies an axial force to move the slips into biting engagement with the casing.
U.S. Pat. No. 4,548,264 discloses a high temperature packer which is set by rotating the running string clockwise or to the right from the surface. Sufficient rotational torque shears pins that allows shoulders to contact respective abutments. The torque transmitting features allow the setting force to be applied by simply rotating the running string to the right. No J-slot mechanism is utilized. Torque is transmitted through sliding dogs causing the setting nut to move downward with respect to a lower cone. U.S. Pat. No. 4,903,777 discloses a dual seal packer which is set by rotating the running string to the right with tension on the string. When rotating the string to the right, left-hand threads on the mandrel work up the internally threaded surface of a running ring, thereby moving the mandrel upward with respect to the cage. Right-hand threads on the ratchet engage an internally threaded surface of the setting ring, and contact of the expander ring with the tapered surface of the slips causes the teeth to engage the casing.
U.S. Pat. No. 4,388,971 discloses a tubing hanger wherein a plurality of spring biased dogs carried by the running tool snap into engagement with cooperating internal grooves formed in the bore of the tubular body of the tool. A radial pin moves upward into the top end of an L-shaped slot so that the work string may be rotated to the right, causing the radial pin to move out of the slot, so that the cone may be moved downward relative to the slips to move the slips outward. The tool may be released by unthreading a connecting nut from the internal threads on the upper body section of the tubing hanger. U.S. Pat. No. 4,598,744 discloses a setting tool with retractable collet fingers. When the tool is made up at the surface, a setting nut is in engagement with a setting sleeve extension by right-hand connecting threads. A mandrel is biased by a coil spring, and a shear pin keeps the mandrel with the latch ring when in the run-in position.
A significant deficiency with prior art tools is the difficulty associated with reliably and not prematurely releasing the slips due to vertical manipulation of the running string (commonly coupled with some limited rotation of the running string), particularly when vertical manipulation is used to set the slips once the slip setting mechanism is released. A tool promoted by Baker Hughes, Inc. under Product No. 292-40/292-65 is believed to be intended to release the slip setting mechanism by merely rotation of the running string with no vertical movement, with vertical movement then being used to subsequently set the slips by moving the cone relative to the slips after the slip setting mechanism is released. A rotatable version of the tool is offered by Baker Hughes under Product No. 292-41/292-66.
While downhole tools which are secured in a well have been released from a run-in position to the released position by rotation of the work string, most mechanisms for accomplishing this release are very complex. Complex mechanisms not only reduce the reliability and increase the cost of the tools, but conventionally downhole tools such as liner hangers have a sizable bore, so that the annular spacing between the OD of a casing and the ID of the liner hanger may be very limited. Other tools do not use set-down weight to move the slips from the released position to the set position, and instead use less reliable or more costly techniques to set the tool in the well.
The disadvantages of the prior art are overcome by the present invention, and an improved gripping tool is hereinafter disclosed which utilizes a reliable mechanism to move the slip setting mechanism from the run-in position to the released position, so that set down weight thereafter may be easily applied to set the gripping tool in the well. Opposing rotation of the work string does not damage the tool due to a rachet mechanism provided in the tool according to the present invention.
The gripping tool according to the present invention may be moved from the run-in position to the released position for setting the slips by merely rotating the running string to the desired direction, e.g., to the right. Once rotated to release the slip setting mechanism, set down weight may then be used to set the slips by moving the cone axially with respect to the slips. Most importantly, a ratchet mechanism is provided so that any reverse rotation of the running string, which may be due to backlash or for other reasons, does not damage the slip setting mechanism on any other part of the downhole gripping tool.
It is an object of the present invention to provide a gripping tool for lowering within a well on a running string, with a gripping tool including a drag member, a plurality of slips, a slip setting mechanism, and a cone member axially moveable relative to the slips to move the slips radially outward to a set position for gripping the borehole wall. At least one ramp is secured to one of the running string or the outer tool body, and moves the slip setting mechanism to a released position when the running string is rotated in a first direction. A ratchet member allows rotation of the slip setting mechanism with respect to the at least one ramp when the running string is rotated in the first direction, and rotationally releases the slip setting mechanism from the running string when the running string is rotated in an opposing second direction.
A related feature of the present invention is a method of using a gripping tool as discussed above. After positioning the tool at a desired depth within a well, the running string may be rotated to move the slip setting mechanism to the released position. If the tubing string rotates in the opposing direction, a ratchet member rotationally releases the slip setting mechanism from the running string.
It is a feature of the present invention that the circumferentially spaced slips may each be provided in a pocket in the outer tool body, thus substantially reducing the likelihood of the slip prematurely moving radially outward from the run-in position. A related feature of the invention is that the slips need not move relative to the outer tool body during the process of moving to the slip setting mechanism from the run-in position to the released position.
A significant feature of the present invention is that a downhole gripping tool may be set in a well, with the tool including circumferentially spaced slips which are moved from the run-in position to a released position for setting the slips due to only rotation of the work string. Reliability of the tool is significantly increased by providing a ratchet mechanism which prevents rotation of the running string in the opposite direction from damaging the slip setting mechanism. The ratchet mechanism is provided between the slip setting mechanism and one of the outer tool body and the inner mandrel.
Another feature of the invention is that the outer tool body may be a cage which axially and circumferentially fixes the slips with respect to the cage. The slip setting mechanism may include axial extending collet fingers which engage a stop surface on the mandrel or the outer tool body. The collet fingers may have a negative angle run-in surface for engagement with a mating negative angle stop surface.
A further feature of the invention is that the ratchet mechanism may include a plurality of torque transmitting surfaces each for engagement with one of the outer tool body and the inner mandrel or barrel when the running string is rotated in the first direction, and a plurality of torque releasing surfaces each for engagement with one of the outer tool body and the inner mandrel when the running tool is rotated in the opposing second direction.
Yet another feature of the invention is that a radially outer surface secured to one of the mandrel and the outer tool body may be provided for maintaining the slip setting mechanism radially in the released position in response to rotation of the work string in a first direction, and an overhang surface radially spaced from the ramp prevents the slip setting mechanism from returning to the run-in position during rotation of the running string in the first direction.
Another feature of the invention is that the downhole tool may utilize vertical manipulation of the work string to release the slips from the set position back to the run-in position.
Another feature of the invention is that the downhole tool may be reliably set, then may be released and subsequently re-set without returning the tool to the surface. Damage to the collet fingers is prevented when the running string is rotated in the opposite direction from that used to release the slip setting mechanism.
An advantage of the invention is that the downhole gripping tool may be manufactured at a relatively low cost, and is highly reliable. Another advantage of the invention is that the gripping tool may be used as a liner hanger, a packer, or an anchor in a well.
Yet another advantage of the invention is that technique for operating the gripping tool is relatively simple, thereby increasing reliability. Even if the gripping tool were to be prematurely set while positioning the tool in a well, the gripping tool may be easily unset and returned to the run-in position.
These and further objects, features, and advantages of the present invention will become apparent in the following detailed description, when reference is made in the figures in the accompanying drawings.